A. Miyamoto

A study of K−π+ scattering in the reaction K−p→K−π+n at 11 GeV/c

Results from a high statistics study of the reaction K−p→K−π+n are presented. These results are based on data obtained with an 11 GeV/c beam using the LASS spectrometer at SLAC. The mass dependence of the spherical harmonic moments provides clear evidence for the production of the complete leading orbitally excited K∗ series up through JP = 5−. These moments are used to perform an energy independent partial wave analysis of the K−π+ system from threshold to 2.6 GeV/c2 using a t-dependent parametrization of the production amplitudes. The amplitudes corroborate the leading K∗(892), K2∗(1430), K3∗(1780), K4∗(2060), and K5∗(2380) resonances observed directly in the moments, and also provide new evidence for underlying states. The 0+ amplitude contains the K0∗(1350) and a second 0+K∗(1950) at higher mass. The 1−K∗(1790) seen earlier two and three-body analyses is confirmed, and evidence is provided for suppressed K−π+ decay mode of a second 1− state, the K∗(1410), which has been seen in earlier three-body analyses.

A study of the Ks0Ks0 system in the reaction K−p→Ks0Ks0Λ at 11 GeV/c

Abstract A 4.1 event/nb sample of 11 GeV/c K−p interactions in the LASS spectrometer at SLAC has been used in an analysis of the exclusive Ks0Ks0Λ final state. The Ks0Ks0 mass distribution exhibits a small cluster of events near threshold, but the mass spectrum is dominated by the f2′(1525), which an amplitude analysis shows to be produced by both natural and unnatural parity exchange. This analysis also provides evidence for an S-wave state in the f2′(1525) region, while production of the f2(1720) is not observed. However, there is structure at ∼ 2.2 GeV/c2 which is similar in shape to that observed in the region of the X(2220) in radiative J/ψ decay; an analysis of the angular distribution indicates a spin of at least 2 in this region. This, together with results from other analyses, indicates that the X(2220) may be the 2++ or 4++, mainly s s , state expected near this mass in the conventional quark model.

Evidence for two strangeonium resonances with JPC=1++ and 1+− in K−p interactions at 11 GeV/c☆

Abstract The results of a partial wave analysis of the low mass KKπ system produced in the reactions K − p →K 0 s K ± π ± Λ at 11 GeV/ c using the LASS spectrometer are presented. Evidence is given for two ss axial-vector meson states: one with quantum numbers J PC = 1 ++ , mass ∼ 1530 MeV/ c 2 , and width ∼ 100 MeV/ c 2 , and the other with quantum numbers J PC =1 +− , mass ∼ 1380 MeV/ c 2 , and width ∼ 80 MeV/ c 2 . These states are good candidates to be the mostly strangeonium members of the ground state 1 ++ and 1 +− nonets predicted by the quark model.

The strange meson resonances observed in the reaction K−p → K0π+π−n at GeV/c

Abstract A model incorporating K ∗ resonance contributions and simple backgrounds is shown to quantitatively reproduce the mass dependence of the partial wave amplitudes governing the production and decay of the K 0 π + π − system. A fit of this model to these amplitudes confirms the resonance interpretations of the well-established 1 + K 1 (1400), the 2 + K 2 ∗ (1430), the 3 − K 3 ∗ (1780), and the less well-known 1 − states, the K ∗ (1410) and the K ∗ (1790). The 4 + amplitudes are shown to be consistent with the production and decay of the 4 + K 4 ∗ (2060). A second 2 + enhancement at a mass of ∼ 1.95 GeV/ c 2 can be interpreted as resonant and may be the radial excitation of the K 2 ∗ (1430) or the triplet partner of the K 4 ∗ (2060). New measurements of the masses, widths and branching ratios of these states are given, and the implications of these data for the spectroscopy of the non-strange meson sector are discussed.

Evidence for A JPC=4++ KK state at ∼2.2 GeV/c2 from K−p interactions at 11 GeV/c

Abstract Data from the reaction K − p→K − K + Λ at 11 GeV/ c have been obtained in the LASS spectrometer at SLAC. A spherical harmonic moments analysis of the K − K + system provides evidence for a rather narrow J PC =4 ++ state at ∼2.2 GeV/ c 2 . Relevant data from the reaction K − p →K 0 s K 0 s Λ in the present experiment are shown also, and comparisons made to results from MARK III and GAMS in this mass region.

Observation of the selective coupling of K* states to the K−η channel☆

Abstract The K−η effective mass spectrum in the reaction K−p→K−π+π−π0p at 11 GeV/c has a prominent peak at ≈1.75 GeV/c2, which is shown to be due to the K3∗(1780) by a spherical harmonic moments analysis and amplitude decomposition; there is no significant signal for K2∗(1430). The measured branching fractions for the leading L=1 and L=2 K∗,s, [BF(K2∗ (1430)→Kη) BF ( K 3 ∗ (1780)→ Kη )=9.4±3.4%] confirm the SU(3) prediction that the Kη channel couples preferentially to odd spin K*,s.

Measurement of polarized target asymmetry on γp→π+n in the third resonance region

Abstract The polarized target asymmetry for the process γ p→ π + n has been measured for incident photon energies from 0.96 to 1.10 GeV, and pion c.m. production angles between 70 and 160°. π + mesons from a polarized propanediole target were detected by a magnetic spectrometer with scintillation counter hodoscopes. The radiative decay widths of nucleon resonances were found by an amplitude analysis, and are compared with theoretical predictions.

Observation of a new Ω∗- at 2.47 GeVc2 in K-p interactions at 11 GeVc

Abstract Clear evidence is presented for an Ω ∗− resonance of mass 2474±12 MeV c 2 and width 72±33 MeV c 2 in K − p interactions at 11 GeV c . The state is observed in the Ω − π + π − decay mode, and the corresponding inclusive cross section, corrected for Ω − π 0 π 0 decay, is estimated to be 290±90 nb.

Spin-parity determination of the φJ(1850) from K−p interactions at 11 GeV/c☆

Abstract High statistics data from the reactions K−p→K−K+Λ and K−p→Ks0K±π∓Λ at 11 GeV/c have been obtained in the LASS spectrometer at SLAC. Spherical harmonic moment and amplitude analyses of the K−K+ system confirm the existence of the φJ(1850) and demonstrate that its quantum numbers are IG(JPC)=0−(3−−). Evidence for a K∗ K (+c.c.) decay mode is also presented.

Observation of ω∗− production in K−p interactions at 11 GeV/c☆

Abstract Clear evidence is presented for the production of an Ω ∗− resonance of mass 2253±13 MeV/ c 2 and width 81±38 MeV/ c 2 in K − p interactions at 11 GeV/ c . The state is observed in the Ξ (1530)K decay mode, and the corresponding inclusive cross section is estimated to be 630±180 nb. Comparisons are made with theoretical predictions and with similar states observed inhyperon beam induced data.